1. Field of the Invention
The present invention relates to a broadcast receiver and a channel scanning method, and more particularly to a multi-channel broadcast receiver for switching a receive channel at predetermined intervals and a channel scanning method using same.
2. Description of the Related Art
In recent years, digital broadcasts have come into service that convert broadcast signals into digital signals and compress the digital signals to transmit them. Such digital broadcasts have less degradation in sound and image compared with conventional television and radio broadcasts. The compression of data as described also enables a digital broadcast to provide multi-channel broadcasts which handle more than one hundred channels. FIG. 7 is a diagram illustrating the construction of a frame in a digital broadcast. This figure shows that broadcast contents including “n” channels are subjected to mapping (in other words, time-division multiplex) in a frame of a predetermined length. In a digital broadcast, contents of this frame are transmitted in sequence, thereby broadcasting “n” channels simultaneously.
As described above, digital broadcasts allow a user to select a desired program from much more programs (channels) than the conventional broadcast media. In such multi-channel digital broadcasts, a scanning function of automatically switching a receive channel at predetermined intervals is of great value as a method of searching for and selecting a desired channel from multiple channels by the user's simple and easy operation of keys.
In a conventional receiver having this scanning function, when a channel scan is instructed by a keystroke of a scan key, the receive channel is automatically switched to another channel at given intervals (hereinafter referred to as a scanning time period) such as 5 seconds or 7 seconds. When a desired channel is found, the broadcast contents of the desired channel are continuously received by re-pressing the scan key. In such cases, if the user sets channels belonging to a desired genre on a setting screen in advance, the channel scan will be carried out within the range of the set channels.
With channel scanning in a conventional receiver, there is a case where the broadcast contents of a channel being currently received, after the channel switching, change during the scanning time period. For example, one piece of music ends and another piece of music begins on one channel within the scanning time period. When this kind of changeover of the broadcast contents occurs, the user cannot accurately identify the broadcast contents or the music provided by the channel being currently received. Then, before the user can identify the broadcast contents, the receive channel is switched to the next channel, thus leading to a disadvantage that the user may miss a program that he or she really wishes to receive (view and/or hear). FIG. 8 explains this kind of case. Referring to this figure, a channel CH1 which was received before a time t1, is switched to a next channel CH2 at the time t1. The channel CH2 changes its broadcast contents M1 to other contents M2 at a time t2 within a scanning time period Ts after the time t1. Then the channel CH2 is also switched to a next channel CH3 at a time t3. Thus, in a case where the broadcast contents change during the scanning time period, it is difficult to identify the broadcast contents of the channel being currently received, resulting in a disadvantage that the receive channel is switched to a next channel before identifying the current broadcast contents thereof.